1. Field of Invention
The present invention relates to a mounting/assembly element for use in the assembly of items, particularly overlapping plate parts and/or components, and comprising a rivet bush with a first end and a second end, and where the first end comprises a deformable zone for insertion through holes lying over each other in the items, and where there is housed a draw-rod in the rivet bush, the first end of which comprises a draw-head with a larger diameter than the draw-rod and a break zone above the draw-head which is housed in the deformable zone of the rivet bush, and where the second end of which extends up over the second end of the rivet bush, and where the second end of the rivet bush comprises an external thread on which there is provided a cooperating nut, said mounting/assembly element being intended for fastening by use of a drawing tool engaged in the draw-rod for breakage in the break zone.
2. Description of Related Art
Such a mounting/assembly element is known from German Patent Application DE 39 02 226 A1, where there is disclosed a mounting assembly element comprising a rivet bush, the insertion end of which comprises a deformation zone, in which rivet bush there is provided a draw-rod comprising a break zone, where the draw-rod by being drawn upon by a drawing tool carries out a deformation of the rivet bush's deformation zone, and with continued traction a breakage occurs in the break zone, so that the pointed end of the draw-rod remains housed inside the rivet bush, the outer walls of which are pressed against the walls of the parts which the mounting element holds assembled. When the mounting assembly element is mounted, i.e., after the draw-rod has broken in the break zone, the break zone of that part of the draw-rod which is connected to the draw-head will be placed in the rivet bush, outside the end of the rivet bush opposite the deformation zone.
The special aspect of this mounting element is that the end of the rivet bush, opposite the deformation zone, extending from the surface of the parts in which the fastening element is mounted, has an external thread on which there is provided a cooperating nut which constitutes the element's contact surface against a surface of a relevant item. The nut can thus be loosened, whereby the item which is fastened by means of one or more of said fastening elements, can be dismounted and mounted with a commonly known hand tool, without the necessity of having to remove/drill-out the rivet bush, and without the necessity of having access to that part of the rivet bush which is fastened in the underlying construction part. Furthermore, the advantage is that the bolt can be used as a form of security-sealing, in that an attempt to loosen the bolt will leave score/scratch marks in the surface of the item fastening by the mounting element.
However, the fastening element disclosed in German Patent Application DE 39 02 226 A1 has the weakness that the rivet bush, in the dismounting and mounting of the nut, can sometimes not withstand the turning moment which is applied to the nut, in that the rivet bush simply turns around with the nut when the turning moment exceeds the frictional force which is established by the fastening of the rivet bush in a relevant hole in the construction in which the mounting element forms part. To counter this, the external side of the deformation zone of the rivet bush has been provided with a grooving with the object of improving the anchoring of the rivet bush in a hole arranged in a relevant item/plate part, so that the ability of the rivet bush to withstand the turning moment is increased.
This, however, has proved to be inadequate, and in the use of said known mounting element, it has thus not been possible to establish sufficient resisting moment to be able to dismount and remount the nut on the element without the rivet bush turning around in its seating in the lowermost construction part. Also, the mounting element has not found application with more strength-demanding fastenings. Moreover, the mounting element will not be suitable for fastening/mounting of parts on locations where vibrations arise, e.g., on machine parts where use is sometimes made of locking fluid to ensure that the nut remains in the preferred position.
From U.S. Pat. No. 4,560,312, there is known a fastening element comprising a threaded draw-rod, the end of which opposite the thread comprises a draw-bar and a bush comprising a deformable zone in the one end and a contact flange in the other end, for inserting through overlapping holes in construction elements which are to be assembled, where the flange is intended for contact respectively with a facing surface of the construction elements, and a nut on the threaded draw-rod, arranged for the tightening of the draw-bar so that the deformation zone of the bush is deformed by the draw-bar, whereby the flange is pressed against the facing surface of the construction elements which are thereby assembled. In order to carry out the tightening of the nut, it is necessary to be able to secure the draw-rod, so that, in the threaded end of the draw-rod, there is a recess to accommodate a cooperating insertion too, intended as a counter-hold for turning moments which arise with the tightening of the nut on the draw-rod against the flange on the bush, for deformation of the bush's deformable zone, on the opposite side of the construction elements. The nut can be dismounted by use of the insertion tool.
It is important to understand that the mounting element disclosed in U.S. Pat. No. 4,560,312 only permits its utilization for the assembly or fastening on construction elements providing that a deformation of the bush's deformation zone is carried out by a regular tightening of the nut on the threaded end of the draw-rod, so that the nut is brought into contact with the flange on the bush, whereby the draw-head on the draw-rod with continued tightening of the nut effects a deformation of the bush's deformable zone, and the drawing of this into contact with the side of the construction elements facing away from the flange. This means that, in the mounting of the mounting element, use must be made of a tightening tool for the nut, and also an insertion tool cooperating with the recess for creating the counter-hold necessary for the tightening of the nut. Other things being equal, this will involve a slow, time-consuming and difficult mounting procedure for the mounting element, which will hardly be attractive with the demands for efficiency which are made today in connection with the assembly of construction elements. Moreover, said mounting elements hardly find application in connection with an automated assembly of construction elements, for example in connection with assembly robots.